In electro-magnetic spring clutches of the type exemplified in the United States Patent No. 3,185,276 to Sajovec, Jr., dated May 25, 1965, in which the spring is normally disengaged, the wrap-down angle or the time duration for effecting engagement of the clutch is a factory adjustment which cannot be altered in the field. Other electro-magnetic spring clutches which have movable armatures, but are of the normally engaged type, are disclosed in the U.S. Pat. Nos. 2,976,976 to Parker, dated Mar. 28, 1961; Ford 3,684,068 dated Oct. 31, 1967; and Baer, 3,349,880 dated Oct. 31, 1967. The last mentioned patent reference discloses a clutch having pins interconnecting the armature and control sleeve or collar and passing through enlarged holes in a driven member, output drum or hub, which loose pin and hole interconnection permits, upon energization of the coil, overtravel of the output drum and unwinding of the spring from the input drum to thus effect disengagement of the clutch. In this clutch the duration of wrap-down of the spring is fixed at the factory. Other pin and slot interconnections are shown in the U.S. Pat. Nos. 3,373,851 to Baer, dated Mar. 19, 1968 and Helander, 3,835,972 dated Sept. 17, 1974 for preventing reverse rotation of the output hub or drum upon disengagement of a normally engaged clutch.
Accordingly, it is one of the objects of this invention to provide, in a normally disengaged, electro-magnetic spring clutch, accurate field adjustment of the duration of time for effecting clutch engagement.
It is another object of the present invention to provide a normally disengaged, electro-magnetic spring clutch capable of a broad range of applications without factory reconstruction or adjustment.
It is a further object of this invention to provide a normally disengaged, electro-magnetic spring clutch which is capable of adjustment of the duration of time to effect clutch engagement and is of relatively simple and inexpensive construction.
It is a still further object of the present invention to provide a normally disengaged, electro-magnetic spring clutch which is capable of having its duration of time for effecting engagement after energization changed quickly and easily and without special or complex tools.